Abstract Trophoblast cell lineages build the functional units of the placenta and are important for the anchorage of the embryo to the mother, The development of trophoblast cell lineages starts with the establishment of the trophectoderm (TE), one of the first two cell lineages that are specified during preimplantation mammalian development. Gene knockout studies in mice showed that TEAD4, a member of TEA-domain containing transcription factors, is the master orchestrator of the TE-specific transcriptional program. TEAD4-null mouse embryos do not mature to the blastocyst stage and lack expression of trophoblast stem cells (TSCs) specific factors. To understand TEAD4 function in trophoblast cells, through genome wide analyses we identified direct targets of TEAD4 in mouse TSCs and found that TEAD4 is required to maintain expression of several mTSC- specific genes. However, molecular mechanism, by which TEAD4 establishes and maintains a TE/TSC-specific transcriptional program are poorly understood. Furthermore, our understanding about the functional importance of TEAD4 in the context of trophoblast development in other mammalian species including human is at its infancy. Thus, the goal of this proposal is to test the hypothesis that TEAD4 selectively orchestrates a TSC/trophoblast progenitor cell-specific transcriptional program and this TEAD4-dependent transcriptional mechanism is conserved event in multiple mammalian species including human. We will define global targets of TEAD4 in both rodent TSCs and human trophoblast progenitors; we will identify epigenetic mechanisms that are augmented by TEAD4 within trophoblast chromatin. In addition, we will also test whether novel TEAD4-associated mechanisms balances self- renewal vs. differentiation of TSCs.